1. Field of the Invention
The present invention relates to a device fabrication method and fabrication device, more particularly to a method of forming a prescribed pattern on a substrate using a liquid coating device such as an inkjet recording device, and improvement of the device.
2. Description of the Related Art
Semiconductor devices and other circuit devices are fabricated by forming a circuit pattern, wiring pattern and other functional film patterns on silicon, glass, PET (polyethylene terephthalate), or other substrates. For the fabrication of such devices, a lithography method, for example, has been used. In the lithography method, a photosensitive agent called a xe2x80x9cresistxe2x80x9d is coated on the substrate, a circuit pattern is irradiated and developed, and the circuit pattern is formed by implanting metal ions. This lithography method requires large-scale equipment, such as a vacuum system, and complicated steps. The material utilization efficiency in the lithography method is only several parts per hundred and most material is disposed. Therefore, the fabrication cost is high.
In U.S. Pat. No. 5,132,248, a method of coating liquid where particles are disposed directly on the substrate to be a pattern by an inkjet method, and transforming the pattern into a conductive film pattern by executing heat treatment and laser irradiation, is proposed. According to this method, photolithography is unnecessary, and the processing is dramatically simplified. However, although the patterning by such an inkjet method has a merit where the processing steps are simple and the amount of raw materials to be used is small, appropriate processing must be performed, such as using the later mentioned banks, to control the liquid on the substrate, which makes it difficult to fabricate a conductive pattern having a desired shape.
Japanese Patent Publication No. S59-75205, on the other hand, states that the coating position of the liquid is controlled by forming banks on the substrate and coating functional liquid in the banks. In this method, the banks are still formed by photolithography, which leads to high cost.
It is also known that after forming a pattern with lyophilic sections and repellent sections on a substrate, liquid material is selectively coated on the lyophilic section by a method such as inkjet. The resolution or this inkjet type recording head is fine, such as 400 dpi, so prescribed patterns in a xcexcm order width can be formed without such a facility as a semiconductor factory. With this method, however, the process of forming patterns for the lyophilic sections and repellent sections using masks is required, and if coating is by an inkjet method, then alignment marks and alignment steps for accurately coating liquid on the lyophilic sections are required, which makes the process complicated. Also, since liquid is ejected to the lyophilic sections, liquid droplets spread and it is difficult to make a thick conductive film. It is possible to increase the number of times of ejection to increase the film thickness, but in this case, the repellency of the repellent sections with respect to ink must be quite high so that the ink is contained in the lyophilic patterns. Also the line width of the wiring to be formed is limited to the width of the pattern of a lyophilic section of the substrate.
It is an object of the present invention to provide a functional film pattern forming method which can form fine film patterns with simplified processing steps. It is also an object of the present invention to provide a functional film pattern forming method which rarely causes such defects as disconnection and short circuit, and can form patterns with a large film thickness which are good for exhibiting such functions as electric conduction.
It is another object of the present invention to provide a film pattern forming device which can easily form fine film patterns.
It is still another object of the present invention to provide conductive film wiring which has a large film thickness, good for electric conduction, rarely causes such defects as disconnection and short-circuit, and which can be formed fine.
It is still another object of the present invention to provide an electro-optical device which rarely causes such defects as disconnection and short-circuit of the wiring section and antenna, and can decrease the size and thickness of the device, the electronic device and the non-contact card medium using this electro-optical device.
The pattern forming method according to the present invention is a method or forming a functional film pattern by ejecting liquid containing functional components onto a substrate by inkjet, comprising a step of ejecting the above-mentioned liquid by inkjet onto the substrate having a functional film forming face where the contact angle with respect to the liquid is 30 deg. or more and 60 deg. or less, and a step of transforming the ejected liquid into a functional film by a heat treatment.
If the contact angle is smaller than 30 deg., liquid droplets spread too much on the substrate, which forms a functional film pattern with irregular shapes. And if the contact angle is greater than 60 deg., inkjet liquid droplets ejected onto the substrate are taken into liquid already on the substrate when making contact with the liquid already on the substrate, which causes such defects as disconnection in the functional film pattern.
If liquid is ejected onto the substrate which has appropriate repellency by inkjet, the spread of ejected liquid droplets after attaching to the substrate can be controlled, and a fine and thick functional film pattern can be directly formed, and also such pattern defects as disconnection, caused when inkjet liquid droplets attach to the substrate and are taken into liquid already on the substrate when making contact with the liquid already on the substrate, can be prevented. Also the process can be simple since the step of performing pattern processing on the substrate is not required, and also a desired functional pattern can be easily formed since the shape of the functional film pattern is not limited to the pattern of the substrate, for example, and the line width of the lines can be adjusted by changing the volume of the inkjet liquid droplets by changing the voltage for ejection.
In the step of ejection by inkjet of the above-mentioned pattern forming method, it is preferable that liquid is ejected such that the distance between the center of the inkjet liquid droplets adjacent to each other on the substrate is greater than the sum of the radius of the inkjet liquid droplets attached to the substrate and the radius of the inkjet liquid droplets before attaching to the substrate, and is smaller than double the radius of the inkjet liquid droplets attached to the substrate. If the inkjet liquid droplets are ejected without directly contacting the liquid droplets already attached to the substrate so as to connect with liquid droplets already attached to the substrate by the spread of newly ejected liquid droplets after being attached to the substrate, irregularities generated on the lines due to the shock caused when inkjet liquid droplets directly contact the liquid droplets already attached to the substrate, causing such defects as disconnection, can be prevented. Also if the ejection space is smaller than double the radius of the liquid droplets on the substrate, the status where lines are not formed due to liquid droplets not connecting to each other can be prevented.
In the above-mentioned pattern forming method, it is preferable that the step of ejection by inkjet ejects the liquid such that 1% or more and 10% or less of overlap of the diameter of liquid is formed when the liquid is attached to the substrate. By controlling the overlap to 10% or less, an excessive amount of liquid to be coated per unit length of a line can be prevented, and the generation of bulges can be prevented. By controlling the overlap to 1% or more, no overlap of liquid droplets being generated due to ejection position accuracy errors can be prevented, and the disconnection of a line can be avoided. A bulge is a swollen patch of liquid generated by the gathering of liquid at a certain part of a line, as shown in FIG. 3. Bulges become the cause of the disconnection of a line and a short-circuit with another line.
It is also preferable that the above-mentioned pattern forming method further comprises a step of ejecting the liquid again onto the functional film by inkjet after executing the above-mentioned ejecting step and transformation step. The method further comprises a step of transforming the lately ejected liquid into the functional film by a heat treatment. After the functional film transforming step, the substrate has repellency and the transformed functional film is lyophilic, so by coating the liquid thereon again, the liquid remains on the functional film without flowing onto the substrate, and a functional film pattern with a thicker film can be formed without increasing the line width.
It is also preferable that the above-mentioned pattern forming method further comprises a step or drying the ejected liquid after the above-mentioned ejecting step and before the step of transforming the ejected liquid into the functional film, and a step of ejecting the liquid again by inkjet on the dried liquid. The drying step here is a step of removing a part or all of the solvent, and is performed by a heat treatment at a temperature lower than the functional film transforming step, and with this drying step alone, the function of the functional components cannot be sufficiently or can barely be exhibited. Since the substrate has repellency after the drying step and the dried liquid is lyophilic, a functional film pattern with a thicker film can be formed by coating liquid again thereon. The drying step is performed by a heat treatment at a temperature lower than the functional film transforming step, so the processing time can be decreased and the energy to be used can be decreased compared with the case of ejecting liquid again after the functional film transforming step.
Also it is preferable that the above-mentioned pattern forming method further comprises a surface treatment step for processing the above-mentioned substrate surface to be a functional film forming face where the contact angle with respect to the above-mentioned liquid is 30 deg. or more and 60 deg. or less.
The above-mentioned pattern forming method is suitably used for forming the patterns of conductive film wiring. In this case, it is preferable that the liquid to be ejected by inkjet contains conductive particles.
The pattern forming device according to the present invention is a device for forming a functional film pattern by ejecting liquid containing functional components onto a substrate by inkjet, comprising inkjet ejecting means for ejecting the liquid by inkjet onto a substrate having a functional film forming face where the contact angle with respect to the liquid is 30 deg. or more and 60 deg. or less, and heat treatment means for transforming the ejected liquid into a functional film by a heat treatment. This pattern forming device is suitably used for forming patterns of conductive film wiring by ejecting the liquid containing conductive particles, for example.
The conductive film wiring of the present invention is formed by the above-mentioned pattern forming method. According to this, a conductive film wiring, where the film thickness is thick and is good for electric conduction, such defects as disconnection and short circuit rarely occurs, and fine patterns can be formed, can be provided.
The electro-optical device according to the present invention is comprised of conductive film wiring according to the above-mentioned invention. The electro-optical device according to the present invention is, for example, a liquid crystal display device, an organic electro-luminescent display device, and a plasma display device.
The electronic device according to the present invention is comprised of the electro-optical device according to the present invention.
The non-contact card medium according to the present invention has the conductive film wiring according to the above-mentioned invention as an antenna circuit.
According to these inventions, an electro-optical device which rarely causes such defects as disconnection and short-circuit of wiring sections and antennas, and can decrease size and thickness, and an electronic device and a non-contact card medium using this electro-optical device, can be provided.